A new type of planet, a rocky world that weighs 17 times as much as Earth – and one astronomers previously believed could never form in the universe – has been discovered, the Harvard-Smithsonian Center for Astrophysics (CfA) announced Monday.

Named Kepler-10c, the planet's existence was thought to be impossible because of its size. "Theorists believed such a world couldn't form because anything so hefty would grab hydrogen gas as it grew and become a Jupiter-like gas giant," CfA scientists said in a news release. "This planet, though, is all solids and much bigger than previously discovered 'super-Earths,' making it a 'mega-Earth'."

"This is the Godzilla of Earths!" Dimitar Sasselov, a CfA researcher and director of the Harvard Origins of Life Initiative, said at the announcement of the discovery, which came at Monday's meeting of the American Astronomical Society. "But unlike the movie monster, Kepler-10c has positive implications for life."

The planet is located about 560 light years – or about 3.2 quadrillion miles – from Earth in a constellation named Draco, where it circles a Sun-like star every 45 days. Nearby is another celestial body that CfA scientists describe as a "lava world," Kepler 10-b, that's about three times Earth's weight and orbits the same star much faster – every 20 hours.

Kepler-10c got its name from the spacecraft that discovered it, part of NASA's Kepler Mission that surveys the Milky Way galaxy for neighbors that might resemble Earth – terrestrial planets where liquid water and perhaps even life might exist.

Astronomers are able to spot planets like these by using what is known as the transit method, in which they watch stars in various known systems. When planets pass in front of them, scientists measure the dimming of their light to determine the planets' size and diameter.

But the astronomers didn't known whether it had a solid or gaseous surface until they could measure its mass. Using the Telescopio Nazionale Galileo in the Canary Islands, they found it weighed much more than expected, about 17 times as much as Earth, which meant it must be made up of rocks and other solids.

"Kepler-10c didn't lose its atmosphere over time. It's massive enough to have held onto one if it ever had it," said Xavier Dumusque, the CfA astronomer who led the study. "It must have formed the way we see it now."

Profound implications for the universe as we know it

The system in whch Kepler-10c is located is about 11 billion years old, which means it formed about 3 billion years after the "Big Bang." (Our galaxy, the Milky Way, is thought to be about 13 billion years old.)

That the planet formed at all has "profound implications for the history of the universe and the possibility of life," CfA researchers say. "The early universe contained only hydrogen and helium. Heavier elements needed to make rocky planets, like silicon and iron, had to be created in the first generations of stars. When those stars exploded, they scattered these crucial ingredients through space, which then could be incorporated into later generations of stars and planets."

That's a process that should have taken billions of years, but didn't in the case of Kepler-10c. That shows huge rocks were able to form in the early universe, even during a time when the heavy elements needed to create them were scarce.

"Finding Kepler-10c tells us that rocky planets could form much earlier than we thought," added Sasselov. "And if you can make rocks, you can make life."